Origins of Medicine: Foxglove Plants

Enlarge Image Image Gallery

Think of Foxglove as the Femme Nikita of herbs— beautiful, potentially deadly, and invaluable when used properly. Foxglove contains substances that are among the most potent heart treatment drugs used today, but they can be lethal if used incorrectly.

Despite the danger, physicians and herbalists have long turned to foxglove to treat a variety of disorders, including tuberculosis and edema. But it wasn’t until the twentieth century that health practitioners made the link between foxglove and congestive heart failure (CHF), and that medicines derived from the plant were developed into prescription drugs.

Foxglove contains the cardiac glycosides digitoxin (from Digitalis ­purpurea and D. lantana) and digoxin (from D. lantana). All of foxglove’s glycosides, known collectively as digitalis, increase the force of heart ­contractions, leading to more efficient movement of blood through the heart and giving the heart more resting time between contractions. ­Glycosides also correct abnormal rhythms such as atrial fibrillation and atrial flutter, and act as a diuretic, an effect that arises more from improved ­circulation than from a direct impact on the kidneys.

While such qualities make digitalis a valuable treatment for CHF, it has drawbacks. One is a narrow therapeutic window that allows desired outcomes only within a small dosage range. Amounts higher than the range can be deadly or, at minimum, cause gastrointestinal discomforts such as depressed appetite, nausea, and vomiting; neurological side effects, such as dizziness, fatigue, and hallucinations; and cardiac system problems, including abnormal heart rhythms. To underscore the deadly power digitalis can wield, between 1993 and 1995, four previously healthy men, including a twenty-three-year-old and a twenty-six-year-old, died after taking an aphrodisiac that left abnormally high amounts of digoxin in their blood.

In addition, foxglove is by itself a poison­ous plant. Do NOT eat it out of your garden, nor try to make your own medicines from it. And use ­digitalis-derived medicines only as recommended by your physician, who will carefully monitor you for ill effects. Practitioners who emphasize natural healing usually prefer to bolster a failing heart with other, milder herbs, notably hawthorn (Crataegus spp).